Aggressiveness of Verticillium dahliae isolates from potato to artichoke

Verticillium wilt caused by Verticillium dahliae is now recognized as one of the major problems limiting yield in artichoke crops in Eastern Spain. Potato is a common crop repeatedly employed in the rotation regimes with artichoke at the Comunidad Valenciana. Since 2002, potato crops in Alicante province, showing symptoms of early senescence of the foliage, had been found widely infested with V. dahliae. Although V dahliae isolates may potentially infect a wide range of hosts, they are considered to be host-adapted, often being virulent only on certain hosts. Since information on the pathogenic behaviour of V. dahliae isolates from potato in Spain is lacking, the present work was carried out to study the pathogenicity of V. dahliae isolates from potato to artichoke. Twelve V. dahliae isolates from potato obtained at different locations in Alicante province were used in two experiments to assess their virulence on artichoke. In each experiment, ten artichoke seedlings were inoculated by root dipping in a suspension of 106 conidia per mL of each isolate, transplanted and maintained six weeks under greenhouse conditions. Disease progress was evaluated weekly on the basis of severity of foliar symptoms and plant height. The shoot-dried weight and final leaf number of plants was also measured at the end of the experiments. All the isolates were able to induce symptoms in artichoke plants, causing various degrees of wilt. Growth was also affected, as showed by reduction of dry weight and stem length of inoculated plants compared whit non-inoculated ones, with significant differences among isolates. These results showed that V dahliae isolates from potato can be very aggressive on artichoke. Since potatoes are considered suitable hosts to spread the fungus by contaminated tuber seed and to build up inoculum levels in the soil, prior potato cultivation might contribute to increase Verticillium wilt risks to future plantings of globe artichoke.